Learning Java Program

import java.util.Stack;
class TestStack 

{
      public static void main(String args[]) 

      {
            Stack mystack1 = new Stack();
            Stack mystack2 = new Stack();
                  // push some numbers onto the stack
            for(int i=0; i<10; i++)
                  mystack1.push(i);
            for(int i=10; i<20; i++)
                  mystack2.push(i);
                  // pop those numbers off the stack
            System.out.println("Stack in mystack1:");
                  for(int i=0; i<10; i++)
            System.out.println(mystack1.pop());
           

            System.out.println("Stack in mystack2:");
                  for(int i=0; i<10; i++)
            System.out.println(mystack2.pop());
      }
}

Stack in mystack1:
9
8
7
6
5
4
3
2
1
0
Stack in mystack2:
19
18
17
16
15
14
13
12
11
10